FIG. 3 shows a vertical section of a conventional disintegrator 1, in which in a case 4 having an upper hopper 2 and under exit 3, there are provided with a pair of upper rolls 5 and 6, an under roll 7 located below the upper rolls, and knives 8 and 9 (9 is prepared for reverse rotation of under roll) projecting from inner surface of case 4 toward the under roll 7. Disintegrative materials 10 thrown inside the hopper 2 are disintegrated between the upper rolls 5, 6 driven as arrows while moving downward, then after disintegrated between the under roll 7 and knives 8, 9, and exited downward from the exit 3.
As shown in FIG. 4, under roll 7 is provided with six cutting edge blocks 14 each of which is fastened by bolts 15 on one of hexagonal installation seats 13 circumferentially formed on outer surface of cylindrical tubular body 12. The construction in the FIGS. 3 and 4 are generally shown in Japanese Examined Patent Application 2(1990)-38259.
FIG. 5 shows another conventional structure corresponding to a view of arrow V in the FIG. 3. Upper rolls 5 and 6 in FIG. 5 have helical blades 17 and 18 respectively, then disintegrative materials put between the upper rolls 5 and 6 are driven to the right by the upper roll 5, and to the left by the upper roll 6 thereby sheared by the opposing blades 17 and 18 and fell on the under roll 7. The under roll 7 shown in the FIG. 5 is provided with helical blades 19 and 20 intersecting each other formed integrally on the surface of the under roll, the blades 19 and 20 forming a number of box seats 21 opened radially outwardly. Disintegrative materials are received in the box seats 21 and parts of the materials projecting from the box seats 21 are cut by knives 8 and 9, and most parts remaining in the box seats 21 fall down when the box seats reach lower position. Therefore, the size of the most disintegrated material pieces after passing the disintegrator is determined by longitudinal length L1, circumferential length L2 and the depth L3 of the box seat 21. This results in, when house wastes for example are disintegrated, the longer final bar like pieces such as 100˜120 mm are obtained and such long pieces are not suitable for mixing in the livestock litter. If the length is below 30˜50 mm, as urine of livestock is soaked, rotting is accelerated and easily change into favorable fertilizer, but it is impossible to cut into satisfactory short length. These disadvantages are not avoided by the cutting edge block 14 of FIG. 4.